1. C PROGRAMMING LECTURE 17 th August IIT Kanpur C Course, Programming club, Fall 2008 1 by Deepak Majeti M-Tech CSE mdeepak@iitk.ac.in

2. Recap C Course, Programming club, Fall 2008 2  C is a high-level language.  Writing a C code. {editors like gedit, vi}  Compiling a C code. {gcc –c test.c –o test}  Executing the object code. {./test}

3. Some more basics C Course, Programming club, Fall 2008 3  Keywords char, static, if, while, return..................... Total= about 32  Data Types int, char, float...………..….. Some more later  Arithmetic Operators + (Plus), - (Minus), * (Multiplication), /(Division) ……….…… …. Some more later

4. My first C program! C Course, Programming club, Fall 2008 4 #include // program prints hello world int main() { printf ("Hello world!"); return 0; } Output: Hello world!

5. Example 1 C Course, Programming club, Fall 2008 5 #include // program prints a number of type int int main() { int number = 4; printf (“Number is %d”, number); return 0; } Output: Number is 4

6. Example 2 C Course, Programming club, Fall 2008 6 #include // program reads and prints the same thing int main() { int number ; printf (“ Enter a Number: ”); scanf (“%d”, &number); printf (“Number is %d\n”, number); return 0; } Output : Enter a number: 4 Number is 4

7. more and more C Course, Programming club, Fall 2008 7 #include int main() { /* this program adds two numbers */ int a = 4; //first number int b = 5; //second number int answer = 0; //result answer = a + b; }

8. Note C Course, Programming club, Fall 2008 8 Errors Compilation Compiler generally gives the line number at which the error is present. Run time C programs are sequential making the debugging easier.

9. Some more Data Types C Course, Programming club, Fall 2008 9  Primary : int, float, char  int (signed/unsigned)(2,4Bytes): used to store integers.  char (signed/unsigned)(1Byte): used to store characters  float, double(4,8Bytes): used to store a decimal number.  User Defined:  typedef: used to rename a data type typedef int integer; can use integer to declare an int.  enum, struct, union

10. Some more Arithmetic Operators C Course, Programming club, Fall 2008 10  Prefix Increment : ++a  example: int a=5; b=++a; // value of b=6; a=6;  Postfix Increment: a++  example int a=5; b=a++; //value of b=5; a=6;

11. Contd… C Course, Programming club, Fall 2008 11  Modulus (remainder): %  example: 12%5 = 2;  Assignment by addition: +=  example: int a=4; a+=1; //(means a=a+1) value of a becomes 5 Can use -, /, *, % also

12. Contd… C Course, Programming club, Fall 2008 12  Comparision Operators:, =, !=, ==, !, &&, ||.  example: int a=4, b=5; a<b returns a true(non zero number) value.  Bitwise Operators: >, ~, &, |,^.  example int a=8; a= a>>1; // value of a becomes 4

13. Operator Precedence C Course, Programming club, Fall 2008 13  Meaning of a + b * c ? is it a+(b*c) or (a+b)*c ?  All operators have precedence over each other  *, / have more precedence over +, -.  If both *, / are used, associativity comes into picture. (more on this later)  example : 5+4*3 = 5+12= 17.

14. Precedence Table C Course, Programming club, Fall 2008 14 Highest on top ++ -- (Postfix) ++ -- (Prefix) * / % + - > & | && ||

15. Input / Output C Course, Programming club, Fall 2008 15  printf (); //used to print to console(screen)  scanf (); //used to take an input from console(user).  example: printf(“%c”, ’a’); scanf(“%d”, &a);  More format specifiers %c The character format specifier. %d The integer format specifier. %i The integer format specifier (same as %d). %f The floating-point format specifier. %o The unsigned octal format specifier. %s The string format specifier. %u The unsigned integer format specifier. %x The unsigned hexadecimal format specifier. % Outputs a percent sign.

16. Some more geek stuff C Course, Programming club, Fall 2008 16  & in scanf.  It is used to access the address of the variable used.  example: scanf(%d,&a); we are reading into the address of a.  Data Hierarchy.  example: int value can be assigned to float not vice-versa. Type casting.

17. Home Work C Course, Programming club, Fall 2008 17  Meaning of  Syntax  Semantics of a programming language  Find the Output:  value=value++ + value++;  Value=++value + ++value;  value=value++ + ++value;

18. End of Today’s Lecture C Course, Programming club, Fall 2008 18 Doubts && Queries?

19. THANK YOU C Course, Programming club, Fall 2008 19